Yes you are correct, but Received parameter gives only source ip 
address,  to get source port  rport  parameter must be present in via 
header.
see rfc 3581

-Subramanya

zhang jw wrote:
> Hi,
> i am confused. Cause when server receive a request, it should check the
> sent-by field of top via header. If the address differ from transport which
> the request received,  it should add a 'received' header.But i didn't see
> this in your message.
>
> On 11/16/06, Andre Kirchner <[EMAIL PROTECTED]> wrote:
>   
>> Hi,
>>
>> What I found out is that the server should answer to the host and port
>> specified in the first VIA header. If the message sent to Asterisk was like
>> the following one, Asterisk should answer back to port 5038 of host
>> 192.168.1.103.
>>
>> OPTIONS sip:192.168.0.103 SIP/2.0
>> Via: SIP/2.0/UDP 192.168.1.103:5038;branch=0.0
>> CSeq: 4711 OPTIONS
>>
>> The problem is that Asterisk is not answering to the specified port ( 5038
>> ), but to the port from which the message was sent to it in order to avoid
>> NAT translation problems. It's ignoring the VIA header.
>> A way to solve this conflict and avoid NAT translation problems is to send
>> the message to Asterisk from the same port you specified in the VIA header.
>> In this case, it would still be compatible with SIP proxies that don't
>> ignore the VIA header.
>>
>> Andre
>>
>>
>> ---------------------------------
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